Process for production of biomass from a carbon source

ABSTRACT

The present invention relates to microorganisms genetically engineered to increase yield and/or efficiency of biomass production from a carbon source, such as e.g. glucose. Also included are processes of using the polynucleotides and modified polynucleotide sequences to transform host microorganisms leading to a microorganism with reduced carbon source diversion, i.e. higher yield and/or efficiency of biomass production from a carbon source such as e.g. glucose.

This application is the U.S. national phase under 35 USC 371 of Int'lApplication No. PCT/EP2006/008728, filed 7 Sep. 2006, which designatedthe U.S. and claims priority to European Patent Application No.05021390.9, filed 9 Sep. 2005; the entire contents of each of which arehereby incorporated by reference.

The present invention relates to microorganisms genetically engineeredto increase yield and/or efficiency of biomass production from a carbonsource, such as e.g. glucose. Processes for generating suchmicroorganisms are also provided by the present invention. The inventionalso relates to polynucleotide sequences comprising genes that encodeproteins that are involved in the bioconversion of a carbon source suchas e.g. glucose into biomass. The invention also featurespolynucleotides comprising the full-length polynucleotide sequences ofthe novel genes and fragments thereof, the novel polypeptides encoded bythe polynucleotides and fragments thereof, as well as their functionalequivalents. Also included are processes of using the polynucleotidesand modified polynucleotide sequences to transform host microorganismsleading to a microorganism with reduced carbon source diversion, i.e.higher yield and/or efficiency of biomass production from a carbonsource such as e.g. glucose.

The bioconversion of a carbon source may involve many differentmetabolic routes, and involve several enzymatic steps to generatebiomass, wherein the enzymes may be located in the cytosol, on themembrane or in the periplasmic space of a host cell. Furthermore,transporters may also play an important role in the efficient conversionof a carbon source into biomass.

For instance, in the case of acetic acid bacteria, which are obligateaerobe, gram-negative microorganisms belonging to the genus Acetobacter,Gluconobacter, and Gluconacetobacter, these microorganisms are able tooxidize D-glucose at the periplasmic membrane level to D-gluconate bymeans of a membrane-bound D-glucose dehydrogenase, and transportD-gluconate into the cytosol. D-gluconate can then be phosphorylated bygluconokinase to D-gluconate-6-phosphate. In addition to that, it isbelieved that D-glucose can be directly transported into the cytosol andthen converted into D-gluconate by means of a cytosolic NAD(P)-dependentD-glucose dehydrogenase. Furthermore, D-glucose transported into thecytosol can also be first phosphorylated to D-glucose-6-phosphate byglucokinase and then be dehydrogenated to D-gluconate-6-phosphate.D-gluconate-6-phosphate may enter the pentose phosphate pathway, beingfurther metabolized to produce reducing power in the form of NAD(P)H andtricarboxylic compounds necessary for growth and maintenance.

Proteins, in particular enzymes, that are active in the metabolizationof glucose are herein referred to as being involved in the GlucoseMetabolization System. Such proteins are abbreviated herein as GMSproteins and function in the direct metabolization or bioconversion of acarbon source such as e.g. glucose into biomass.

One disadvantage of such bioconversion processes, however, is thediversion of carbon sources or intermediates throughout saidbioconversion process such that for instance the next (enzymatic) stepcannot be performed in an optimal way, leading to the loss of availablecarbon substrate material for conversion into biomass and resultantenergy losses, in form of e.g. ATP or NADPH. In the case of for instancethe bioconversion of glucose into biomass, this loss may be due totransporting the glucose or an intermediate thereof out of the cytosolor by using the glucose or the resulting intermediates as substrates forother pathways not leading to the production of biomass.

It is an object of the present invention to provide microorganisms whichare engineered in such a way that the carbon source diversion throughoutthe bioconversion of carbon sources, such as e.g. glucose, is altered,e.g. via reduction of carbon source diversion, leading to higherproduction and/or yield of biomass produced from such carbon sources.

Surprisingly, it has now been found that GMS proteins or subunits ofsuch proteins having activity towards or which are involved in thebioconversion of a carbon source such as e.g. glucose play an importantrole in the production of biomass.

In one embodiment, GMS proteins of the present invention are selectedfrom oxidoreductases [EC 1], preferably oxidoreductases acting on theCH—OH group of donors [EC 1.1], more preferably oxidoreductases withNAD⁺ or NADP⁺ as acceptor [EC 1.1.1] and oxidoreductases with a quinoneor similar compound as acceptor [EC 1.1.5], most preferably NADP-glucosedehydrogenase [EC 1.1.1.47] and PQQ dependent glucose dehydrogenase [EC1.1.5.2] or from transferases [EC 2], preferably transferasestransferring phosphorus-containing groups [EC 2.7], more preferablyphosphotransferases with an alcohol group as acceptor [EC 2.7.1], mostpreferably gluconokinase [EC 2.7.1.12].

Furthermore, the GMS proteins or subunits of such proteins havingactivity towards or which are involved in the bioconversion of a carbonsource such as e.g. glucose into biomass are selected from the groupconsisting of membrane-bound PQQ-dependent D-glucose dehydrogenase,NAD(P)-dependent D-glucose dehydrogenase, cytosolic D-glucose kinase,enzymes or enzyme subunits having activity towards or involved in theassimilation of D-gluconate such as membrane-bound FAD-dependentD-gluconate dehydrogenase (2-keto-D-gluconate-forming), membrane-boundPQQ-dependent D-gluconate dehydrogenase (5-keto-D-gluconate-forming),cytosolic D-gluconate kinase, enzymes or enzyme subunits having activitytowards or involved in the assimilation of 2 KD such as membrane-boundFAD-dependent 2-keto-D-gluconate dehydrogenase, NAD(P)-dependentglucose-1-dehydrogenase, flavin containing gluconate-2-dehydrogenase,gluconate-5-dehydrogenase (5-keto-D-gluconate reductase), and cytosolicNAD(P)-dependent 2-keto-D-gluconate reductase.

In particular, it has now been found that GMS proteins encoded bypolynucleotides having a nucleotide sequence that hybridizes preferablyunder highly stringent conditions to a sequence shown in SEQ ID NO:1play an important role in the bioconversion of a carbon source such ase.g. glucose to biomass. It has also been found, that by geneticallyaltering such nucleotides in a microorganism, such as for exampleGluconobacter, the efficiency of said bioconversion within saidmicroorganism can be even greatly improved leading e.g. to higherproduction and/or yield of biomass from a carbon source such as e.g.glucose.

Consequently, the invention relates to a polynucleotide selected fromthe group consisting of:

-   (a) polynucleotides encoding a polypeptide comprising the amino acid    sequence according to SEQ ID NO:2;-   (b) polynucleotides comprising the nucleotide sequence according to    SEQ ID NO:1;-   (c) polynucleotides comprising a nucleotide sequence obtainable by    nucleic acid amplification such as polymerase chain reaction, using    genomic DNA from a microorganism as a template and a primer set    according to SEQ ID NO:3 and SEQ ID NO:4;-   (d) polynucleotides comprising a nucleotide sequence encoding a    fragment or derivative of a polypeptide encoded by a polynucleotide    of any of (a) to (c) wherein in said derivative one or more amino    acid residues are conservatively substituted compared to said    polypeptide, and said fragment or derivative has the activity of a    transferase [EC 2], preferably transferase transferring    phosphorus-containing groups [EC 2.7] (GMS 08);-   (e) polynucleotides the complementary strand of which hybridizes    under stringent conditions to a polynucleotide as defined in any one    of (a) to (d) and which encode a transferase [EC 2], preferably    transferase transferring phosphorus-containing groups [EC 2.7] (GMS    08); and-   (f) polynucleotides which are at least 70%, such as 85, 90 or 95%    homologous to a polynucleotide as defined in any one of (a) to (d)    and which encode a transferase [EC 2], preferably transferase    transferring phosphorus-containing groups [EC 2.7] (GMS 08);-   or-   the complementary strand of such a polynucleotide.

The GMS protein as isolated from Gluconobacter oxydans DSM 17078 shownin SEQ ID NO:2 and described herein was found to be a particularlyuseful GMS protein, since it appeared that it performs a crucialfunction in the bioconversion of a carbon source such as e.g. glucose tobiomass in microorganisms, in particular in bacteria, such as aceticacid bacteria, such as Gluconobacter, Acetobacter and Gluconacetobacter.Accordingly, the invention relates to a polynucleotide encoding apolypeptide according to SEQ ID NO:2. This protein may be encoded by anucleotide sequence as shown in SEQ ID NO:1. The invention thereforealso relates to polynucleotides comprising the nucleotide sequenceaccording to SEQ ID NO:1.

The nucleotide and amino acid sequences determined above were used as a“query sequence” to perform a search with Blast2 program (version 2 orBLAST from National Center for Biotechnology [NCBI] against the databasePRO SW-SwissProt (full release plus incremental updates). From thesearches, the GMS 08 polynucleotide according to SEQ ID NO:1 wasannotated as encoding a protein having gluconate kinase activity.

A nucleic acid according to the invention may be obtained by nucleicacid amplification using cDNA, mRNA or alternatively, genomic DNA, as atemplate and appropriate oligonucleotide primers such as the nucleotideprimers according to SEQ ID NO:3 and SEQ ID NO:4 according to standardPCR amplification techniques. The nucleic acid thus amplified may becloned into an appropriate vector and characterized by DNA sequenceanalysis.

The template for the reaction may be cDNA obtained by reversetranscription of mRNA prepared from strains known or suspected tocomprise a polynucleotide according to the invention. The PCR productmay be subcloned and sequenced to ensure that the amplified sequencesrepresent the sequences of a new nucleic acid sequence as describedherein, or a functional equivalent thereof.

The PCR fragment may then be used to isolate a full length cDNA clone bya variety of known methods. For example, the amplified fragment may belabeled and used to screen a bacteriophage or cosmid cDNA library.Alternatively, the labeled fragment may be used to screen a genomiclibrary.

Accordingly, the invention relates to polynucleotides comprising anucleotide sequence obtainable by nucleic acid amplification such aspolymerase chain reaction, using DNA such as genomic DNA from amicroorganism as a template and a primer set according to SEQ ID NO:3and SEQ ID NO:4.

The invention also relates to polynucleotides comprising a nucleotidesequence encoding a fragment or derivative of a polypeptide encoded by apolynucleotide as described herein wherein in said derivative one ormore amino acid residues are conservatively substituted compared to saidpolypeptide, and said fragment or derivative has the activity of a GMSpolypeptide, preferably a GMS 08 polypeptide.

The invention also relates to polynucleotides the complementary strandof which hybridizes under stringent conditions to a polynucleotide asdefined herein and which encode a GMS polypeptide, preferably a GMS 08polypeptide.

The invention also relates to polynucleotides which are at least 70%identical to a polynucleotide as defined herein and which encode a GMSpolypeptide; and the invention also relates to polynucleotides being thecomplementary strand of a polynucleotide as defined herein above.

The invention also relates to primers, probes and fragments that may beused to amplify or detect a DNA according to the invention and toidentify related species or families of microorganisms also carryingsuch genes.

The present invention also relates to vectors which includepolynucleotides of the invention and microorganisms which aregenetically engineered with the polynucleotides or said vectors.

The invention also relates to processes for producing microorganismscapable of expressing a polypeptide encoded by the above definedpolynucleotide and a polypeptide encoded by a polynucleotide as definedabove.

The invention also relates to microorganisms wherein the activity of aGMS polypeptide, preferably a GMS 08 polypeptide, is enhanced and/orimproved so that the yield and/or production of biomass which isproduced through bioconversion of a carbon source such as e.g. glucoseis increased.

A suitable carbon source that can be converted into biomass may be forinstance glucose or selected from carbon sources the assimilation ofwhich results in the formation of glucose, in particular D-glucose, suchas sucrose, maltose, starch, cellulose, cellobiose, lactose, isomaltose,dextran, trehalose or mixtures thereof.

The skilled person will know how to enhance and/or improve the activityof a GMS protein, preferably a GMS 08 protein. Such may be for instanceaccomplished by either genetically modifying the host organism in such away that it produces more or more stable copies of the GMS protein,preferably the GMS 08 protein, than the wild type organism or byincreasing the specific activity of the GMS protein, preferably the GMS08 protein.

In the following description, procedures are detailed to achieve thisgoal, i.e. the increase in the yield and/or production of biomass whichis produced through bioconversion of a carbon source such as e.g.glucose by increasing the activity of a GMS 08 protein. These proceduresapply mutatis mutandis for other GMS proteins.

Modifications in order to have the organism produce more copies of theGMS 08 gene and/or protein may include the use of a strong promoter, orthe mutation (e.g. insertion, deletion or point mutation) of (parts of)the GMS 08 gene or its regulatory elements. It may also involve theinsertion of multiple copies of the gene into a suitable microorganism.An increase in the specific activity of a GMS 08 protein may also beaccomplished by methods known in the art. Such methods may include themutation (e.g. insertion, deletion or point mutation) of (parts of) theGMS 08 gene. A gene is said to be “overexpressed” if the level oftranscription of said gene is enhanced in comparison to the wild typegene. This may be measured by for instance Northern blot analysisquantifying the amount of mRNA as an indication for gene expression. Asused herein, a gene is overexpressed if the amount of generated mRNA isincreased by at least 1%, 2%, 5% 10%, 25%, 50%, 75%, 100%, 200% or evenmore than 500%, compared to the amount of mRNA generated from awild-type gene.

Also known in the art are methods of increasing the activity of a givenprotein by contacting the GMS 08 protein with specific enhancers orother substances that specifically interact with the GMS 08 protein. Inorder to identify such specific enhancers, the GMS 08 protein may beexpressed and tested for activity in the presence of compounds suspectedto enhance the activity of the GMS 08 protein. The activity of the GMS08 protein may also be increased by stabilizing the messenger RNAencoding GMS 08. Such methods are also known in the art, see forexample, in Sambrook et al., 1989, Molecular Cloning, A LaboratoryManual, Cold Spring Harbor Press, N.Y.; and Ausubel et al. (eds.), 1995,Current Protocols in Molecular Biology, (John Wiley & Sons, N.Y.).

The invention may be performed in any microorganism carrying a GMS 08gene or equivalent or homologue thereof. Suitable microorganisms may beselected from the group consisting of yeast, algae and bacteria, eitheras wild type strains, mutant strains derived by classic mutagenesis andselection methods or as recombinant strains. Examples of such yeast maybe, e.g., Candida, Saccharomyces, Zygosaccharomyces,Schizosaccharomyces, or Kluyveromyces. An example of such algae may be,e.g., Chlorella. Examples of such bacteria may be, e.g., Gluconobacter,Acetobacter, Gluconacetobacter, Ketogulonicigenium, Pantoea,Pseudomonas, such as, e.g., Pseudomonas putida, and Escherichia, suchas, e.g., Escherichia coli. Preferred are Gluconobacter or Acetobacteraceti, such as for instance G. oxydans, G. cerinus, G. frateurii, A.aceti subsp. xylinum or A. aceti subsp. orleanus, preferably G. oxydansDSM 17078. Gluconobacter oxydans DSM 17078 (formerly known asGluconobacter oxydans N44-1) has been deposited at Deutsche Sammlung vonMikroorganismen und Zellkulturen (DSMZ), Mascheroder Weg 1B, D-38124Braunschweig, Germany according to the Budapest Treaty on 26. Jan. 2005.

Microorganisms which can be used for the present invention may bepublicly available from different sources, e.g., Deutsche Sammlung vonMikroorganismen und Zellkulturen (DSMZ), Mascheroder Weg 1B, D-38124Braunschweig, Germany, American Type Culture Collection (ATCC), P.O. Box1549, Manassas, Va. 20108 USA or Culture Collection Division, NITEBiological Resource Center, 2-5-8, Kazusakamatari, Kisarazu-shi, Chiba,292-0818, Japan (formerly: Institute for Fermentation, Osaka (IFO),17-85, Juso-honmachi 2-chome, Yodogawa-ku, Osaka 532-8686, Japan).Examples of preferred bacteria deposited with IFO are for instanceGluconobacter oxydans (formerly known as G. melanogenus) IFO 3293,Gluconobacter oxydans (formerly known as G. melanogenus) IFO 3292,Gluconobacter oxydans (formerly known as G. rubiginosus) IFO 3244,Gluconobacter frateurii (formerly known as G. industrius) IFO 3260,Gluconobacter cerinus IFO 3266, Gluconobacter oxydans IFO 3287, andAcetobacter aceti subsp. orleanus IFO 3259, which were all deposited onApr. 5, 1954; Acetobacter aceti subsp. xylinum IFO 13693 deposited onOct. 22, 1975, and Acetobacter aceti subsp. xylinum IFO 13773 depositedon Dec. 8, 1977. Strain Acetobacter sp. ATCC 15164, which is also anexample of a preferred bacterium, was deposited with ATCC. StrainGluconobacter oxydans (formerly known as G. melanogenus) N 44-1 asanother example of a preferred bacterium is a derivative of the strainIFO 3293 and is described in Sugisawa et al., Agric. Biol. Chem. 54:1201-1209, 1990.

A microorganism as of the present invention may carry furthermodifications either on the DNA or protein level (see above), as long assuch modification(s) has/have a direct impact on the yield, productionand/or efficiency of biomass from a substrate such as e.g. glucose. Suchfurther modifications may for instance affect other genes encodingoxidoreductases or isomerases as described above, in particular genesencoding NAD(P)-glucose dehydrogenase, PQQ-dependent glucosedehydrogenase, FAD-dependent gluconate-2-dehydrogenase,NAD(P)-gluconate-2-dehydrognease, gluconate-5-dehydrogenase,2-ketogluconate dehydrogenase, 2,5-di-ketogluconate dehydrogenase,gluconate oxidase, phosphoglucoseisomerase, or further genes encodingenzymes involved in the pentose phosphate pathway, such as for instance6-phosphogluconate dehydrogenase, 6-phosphogluconolactonase,ribulose-5-phosphate 3-epimerase, transaldolase or transketolase, orfurther genes encoding enzymes linking the pentose phosphate pathway toother pathways of carbon metabolism, such as for instance6-phosphogluconate dehydratase, fructose-1,6-bisphosphate orphosphofructokinase. In one particular embodiment, such furthermodification may affect the gene coding for membrane-bound PQQ-dependentglucose dehydrogenase activity, wherein the activity of such gene isreduced or nullified.

A preferred gene coding for such membrane-bound PQQ-dependent glucosedehydrogenase is shown in SEQ ID NO:11 or a gene which is at least 70,80, 90, or 98% identical. Methods of performing such modifications areknown in the art, with some examples further described herein.

In accordance with a further object of the present invention there isprovided the use of a polynucleotide as defined above or a microorganismwhich is genetically engineered using such polynucleotides in theefficient production of biomass from a carbon source.

The invention also relates to processes for the expression of endogenousgenes in a microorganism, to processes for the production ofpolypeptides as defined above in a microorganism and to processes forthe production of microorganisms capable of growth on a given carbonsource such as e.g. glucose. All these processes comprise the step ofaltering a microorganism, wherein “altering” as used herein encompassesthe process for “genetically altering” or “altering the composition ofthe cell culture media and/or methods used for culturing” in such a waythat the yield and/or productivity of biomass can be improved comparedto the wild-type organism. As used herein, “improved yield of biomass”means an increase of at least 5%, 10%, 25%, 30%, 40%, 50%, 75%, 100%,200% or even more than 500%, depending on the carbon source used forgrowth, compared to a wild-type microorganism, i.e. a microorganismwhich is not genetically altered.

The term “genetically engineered” or “genetically altered” means thescientific alteration of the structure of genetic material in a livingorganism. It involves the production and use of recombinant DNA. More inparticular it is used to delineate the genetically engineered ormodified organism from the naturally occurring organism. Geneticengineering may be done by a number of techniques known in the art, suchas e.g. gene replacement, gene amplification, gene disruption,transfection, transformation using plasmids, viruses, or other vectors.A genetically modified organism, e.g. genetically modifiedmicroorganism, is also often referred to as a recombinant organism, e.g.recombinant microorganism.

Advantageous embodiments of the invention become evident from thedependent claims. These and other aspects and embodiments of the presentinvention should now be apparent to those skilled in the art based onthe teachings herein.

The sequence of the gene comprising a nucleotide sequence according toSEQ ID NO:1 encoding a GMS 08 protein was determined by sequencing agenomic clone obtained from Gluconobacter oxydans DSM 17078.

The invention also relates to a polynucleotide encoding at least abiologically active fragment or derivative of a GMS 08 polypeptide asshown in SEQ ID NO:2.

As used herein, “biologically active fragment or derivative” means apolypeptide which retains essentially the same biological function oractivity as the polypeptide shown in SEQ ID NO:2. Examples of biologicalactivity may for instance be enzymatic activity, signaling activity orantibody reactivity activity. The term “biological function” or“functional equivalent” as used herein means that the protein hasessentially the same biological activity, e.g. enzymatic, signaling orantibody reactivity activity, as a polypeptide shown in SEQ ID NO:2.

The polypeptides and polynucleotides of the present invention arepreferably provided in an isolated form, and preferably are purified tohomogeneity.

The term “isolated” means that the material is removed from its originalenvironment (e.g., the natural environment if it is naturallyoccurring). For example, a naturally-occurring polynucleotide orpolypeptide present in a living microorganism is not isolated, but thesame polynucleotide or polypeptide, separated from some or all of thecoexisting materials in the natural system, is isolated. Suchpolynucleotides could be part of a vector and/or such polynucleotides orpolypeptides could be part of a composition and still be isolated inthat such vector or composition is not part of its natural environment.

An isolated polynucleotide or nucleic acid as used herein may be a DNAor RNA that is not immediately contiguous with both of the codingsequences with which it is immediately contiguous (one on the 5′-end andone on the 3′-end) in the naturally occurring genome of the organismfrom which it is derived. Thus, in one embodiment, a nucleic acidincludes some or all of the 5′-non-coding (e.g., promoter) sequencesthat are immediately contiguous to the coding sequence. The term“isolated polynucleotide” therefore includes, for example, a recombinantDNA that is incorporated into a vector, into an autonomously replicatingplasmid or virus, or into the genomic DNA of a prokaryote or eukaryote,or which exists as a separate molecule (e.g., a cDNA or a genomic DNAfragment produced by PCR or restriction endonuclease treatment)independent of other sequences. It also includes a recombinant DNA thatis part of a hybrid gene encoding an additional polypeptide that issubstantially free of cellular material, viral material, or culturemedium (when produced by recombinant DNA techniques), or chemicalprecursors or other chemicals (when chemically synthesized). Moreover,an “isolated nucleic acid fragment” is a nucleic acid fragment that isnot naturally occurring as a fragment and would not be found in thenatural state.

As used herein, the terms “polynucleotide”, “gene” and “recombinantgene” refer to nucleic acid molecules which may be isolated fromchromosomal DNA, which include an open reading frame encoding a protein,e.g. G. oxydans DSM 17078 GMS proteins. A polynucleotide may include apolynucleotide sequence as shown in SEQ ID NO:1 or fragments thereof andregions upstream and downstream of the gene sequences which may include,for example, promoter regions, regulator regions and terminator regionsimportant for the appropriate expression and stabilization of thepolypeptide derived thereof.

A gene may include coding sequences, non-coding sequences such as forinstance untranslated sequences located at the 3′- and 5′-ends of thecoding region of a gene, and regulatory sequences. Moreover, a generefers to an isolated nucleic acid molecule as defined herein. It isfurthermore appreciated by the skilled person that DNA sequencepolymorphisms that lead to changes in the amino acid sequences of GMSproteins may exist within a population, e.g., the Gluconobacter oxydanspopulation. Such genetic polymorphism in the GMS 08 gene may exist amongindividuals within a population due to natural variation or in cellsfrom different populations. Such natural variations can typically resultin 1-5% variance in the nucleotide sequence of the GMS 08 gene. Any andall such nucleotide variations and the resulting amino acid polymorphismin GMS 08 are the result of natural variation and that do not alter thefunction or biological activity of GMS proteins are intended to bewithin the scope of the invention.

As used herein, the terms “polynucleotide” or “nucleic acid molecule”are intended to include DNA molecules (e.g., cDNA or genomic DNA) andRNA molecules (e.g., mRNA) and analogs of the DNA or RNA generated usingnucleotide analogs. The nucleic acid molecule may be single-stranded ordouble-stranded, but preferably is double-stranded DNA. The nucleic acidmay be synthesized using oligonucleotide analogs or derivatives (e.g.,inosine or phosphorothioate nucleotides). Such oligonucleotides may beused, for example, to prepare nucleic acids that have alteredbase-pairing abilities or increased resistance to nucleases.

The sequence information as provided herein should not be so narrowlyconstrued as to require inclusion of erroneously identified bases. Thespecific sequences disclosed herein may be readily used to isolate thecomplete gene from a microorganism capable of converting a given carbonsource such as e.g. glucose into biomass, in particular Gluconobacteroxydans, preferably Gluconobacter oxydans DSM 17078 which in turn mayeasily be subjected to further sequence analyses thereby identifyingsequencing errors.

Unless otherwise indicated, all nucleotide sequences determined bysequencing a DNA molecule herein were determined using an automated DNAsequencer and all amino acid sequences of polypeptides encoded by DNAmolecules determined herein were predicted by translation of a DNAsequence determined as above. Therefore, as is known in the art for anyDNA sequence determined by this automated approach, any nucleotidesequence determined herein may contain some errors. Nucleotide sequencesdetermined by automation are typically at least about 90% identical,more typically at least about 95% to at least about 99.9% identical tothe actual nucleotide sequence of the sequenced DNA molecule. The actualsequence may be more precisely determined by other approaches includingmanual DNA sequencing methods well known in the art. As is also known inthe art, a single insertion or deletion in a determined nucleotidesequence compared to the actual sequence will cause a frame shift intranslation of the nucleotide sequence such that the predicted aminoacid sequence encoded by a determined nucleotide sequence will becompletely different from the amino acid sequence actually encoded bythe sequenced DNA molecule, beginning at the point of such an insertionor deletion.

The person skilled in the art is capable of identifying such erroneouslyidentified bases and knows how to correct for such errors.

A nucleic acid molecule according to the invention may comprise only aportion or a fragment of the nucleic acid sequence provided by thepresent invention, such as for instance the sequence shown in SEQ IDNO:1, for example a fragment which may be used as a probe or primer suchas for instance SEQ ID NO:3 or SEQ ID NO:4 or a fragment encoding aportion of a protein according to the invention. The nucleotide sequencedetermined from the cloning of the GMS 08 gene allows for the generationof probes and primers designed for use in identifying and/or cloningother GMS 08 family members, as well as GMS 08 homologues from otherspecies. The probe/primer typically comprises substantially purifiedoligonucleotides which typically comprises a region of nucleotidesequence that hybridizes preferably under highly stringent conditions toat least about 12 or 15, preferably about 18 or 20, more preferablyabout 22 or 25, even more preferably about 30, 35, 40, 45, 50, 55, 60,65, or 75 or more consecutive nucleotides of a nucleotide sequence shownin SEQ ID NO:1 or a fragment or derivative thereof.

A nucleic acid molecule encompassing all or a portion of the nucleicacid sequence of SEQ ID NO:1 may be isolated by the polymerase chainreaction (PCR) using synthetic oligonucleotide primers designed basedupon the sequence information contained herein.

A nucleic acid of the invention may be amplified using cDNA, mRNA oralternatively, genomic DNA, as a template and appropriateoligonucleotide primers according to standard PCR amplificationtechniques. The nucleic acid thus amplified may be cloned into anappropriate vector and characterized by DNA sequence analysis.

Fragments of a polynucleotide according to the invention may alsocomprise polynucleotides not encoding functional polypeptides. Suchpolynucleotides may function as probes or primers for a PCR reaction.

Nucleic acids according to the invention irrespective of whether theyencode functional or non-functional polypeptides, may be used ashybridization probes or polymerase chain reaction (PCR) primers. Uses ofthe nucleic acid molecules of the present invention that do not encode apolypeptide having a GMS 08 activity include, inter alia, (1) isolatingthe gene encoding the protein of the present invention, or allelicvariants thereof from a cDNA library, e.g., from other organisms thanGluconobacter oxydans and (2) Northern blot analysis for detectingexpression of mRNA of said protein in specific cells or (3) use inabolishing or altering the function or activity of homologous GMS 08genes in said other organisms.

Probes based on the nucleotide sequences provided herein may be used todetect transcripts or genomic sequences encoding the same or homologousproteins for instance in other organisms. Nucleic acid moleculescorresponding to natural variants and non-G. oxydans homologues of theG. oxydans GMS 08 DNA of the invention which are also embraced by thepresent invention may be isolated based on their homology to the G.oxydans GMS 08 nucleic acid disclosed herein using the G. oxydans DNA,or a portion thereof, as a hybridization probe according to standardhybridization techniques, preferably under highly stringenthybridization conditions.

In preferred embodiments, the probe further comprises a label groupattached thereto, e.g., the label group can be a radioisotope, afluorescent compound, an enzyme, or an enzyme cofactor.

Homologous gene sequences may be isolated, for example, by performingPCR using two degenerate oligonucleotide primer pools designed on thebasis of nucleotide sequences as taught herein.

The template for the reaction may be cDNA obtained by reversetranscription of mRNA prepared from strains known or suspected toexpress a polynucleotide according to the invention. The PCR product maybe subcloned and sequenced to ensure that the amplified sequencesrepresent the sequences of a new nucleic acid sequence as describedherein, or a functional equivalent thereof.

The PCR fragment may then be used to isolate a full length cDNA clone bya variety of known methods. For example, the amplified fragment may belabeled and used to screen a bacteriophage or cosmid cDNA library.Alternatively, the labeled fragment may be used to screen a genomiclibrary.

PCR technology can also be used to isolate full-length cDNA sequencesfrom other organisms. For example, RNA may be isolated, followingstandard procedures, from an appropriate cellular or tissue source. Areverse transcription reaction may be performed on the RNA using anoligonucleotide primer specific for the most 5′-end of the amplifiedfragment for the priming of first strand synthesis.

The resulting RNA/DNA hybrid may then be “tailed” (e.g., with guanines)using a standard terminal transferase reaction, the hybrid may bedigested with RNaseH, and second strand synthesis may then be primed(e.g., with a poly-C primer). Thus, cDNA sequences upstream of theamplified fragment may easily be isolated. For a review of usefulcloning strategies, see e.g., Sambrook et al., supra; and Ausubel etal., supra.

Also, nucleic acids encoding other GMS 08 family members, which thushave a nucleotide sequence that differs from a nucleotide sequenceaccording to SEQ ID NO:1, are within the scope of the invention.Moreover, nucleic acids encoding GMS 08 proteins from different specieswhich thus may have a nucleotide sequence which differs from anucleotide sequence shown in SEQ ID NO:1 are within the scope of theinvention.

The invention also relates to an isolated polynucleotide hybridisableunder stringent conditions, preferably under highly stringentconditions, to a polynucleotide according to the present invention, suchas for instance a polynucleotide shown in SEQ ID NO:1. Advantageously,such polynucleotide may be obtained from a microorganism capable ofconverting a given carbon source such as e.g. glucose into biomass, inparticular Gluconobacter oxydans, preferably Gluconobacter oxydans DSM17078.

As used herein, the term “hybridizing” is intended to describeconditions for hybridization and washing under which nucleotidesequences at least about 50%, at least about 60%, at least about 70%,more preferably at least about 80%, even more preferably at least about85% to 90%, most preferably at least 95% homologous to each othertypically remain hybridized to each other.

In one embodiment, a nucleic acid of the invention is at least 40%, 45%,50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%,96%, 97%, 98%, 99%, or more homologous to a nucleic acid sequence shownin SEQ ID NO:1 or the complement thereof.

A preferred, non-limiting example of such hybridization conditions arehybridization in 6× sodium chloride/sodium citrate (SSC) at about 45°C., followed by one or more washes in 1×SSC, 0.1% SDS at 50° C.,preferably at 55° C., more preferably at 60° C. and even more preferablyat 65° C.

Highly stringent conditions include, for example, 2 h to 4 daysincubation at 42° C. using a digoxigenin (DIG)-labeled DNA probe(prepared by using a DIG labeling system; Roche Diagnostics GmbH, 68298Mannheim, Germany) in a solution such as DigEasyHyb solution (RocheDiagnostics GmbH) with or without 100 μg/ml salmon sperm DNA, or asolution comprising 50% formamide, 5×SSC (150 mM NaCl, 15 mM trisodiumcitrate), 0.02% sodium dodecyl sulfate, 0.1% N-lauroylsarcosine, and 2%blocking reagent (Roche Diagnostics GmbH), followed by washing thefilters twice for 5 to 15 minutes in 2×SSC and 0.1% SDS at roomtemperature and then washing twice for 15-30 minutes in 0.5×SSC and 0.1%SDS or 0.1×SSC and 0.1% SDS at 65-68° C.

Preferably, an isolated nucleic acid molecule of the invention thathybridizes under preferably highly stringent conditions to a nucleotidesequence of the invention corresponds to a naturally-occurring nucleicacid molecule. As used herein, a “naturally-occurring” nucleic acidmolecule refers to an RNA or DNA molecule having a nucleotide sequencethat occurs in nature (e.g., encodes a natural protein). In oneembodiment, the nucleic acid encodes a natural G. oxydans GMS 08protein.

The skilled artisan will know which conditions to apply for stringentand highly stringent hybridization conditions. Additional guidanceregarding such conditions is readily available in the art, for example,in Sambrook et al., 1989, Molecular Cloning, A Laboratory Manual, ColdSpring Harbor Press, N.Y.; and Ausubel et al. (eds.), 1995, CurrentProtocols in Molecular Biology, (John Wiley & Sons, N.Y.). Of course, apolynucleotide which hybridizes only to a poly (A) sequence (such as the3′-terminal poly (A) tract of mRNAs), or to a complementary stretch of T(or U) residues, would not be included in a polynucleotide of theinvention used to specifically hybridize to a portion of a nucleic acidof the invention, since such a polynucleotide would hybridize to anynucleic acid molecule containing a poly (A) stretch or the complementthereof (e.g., practically any double-stranded cDNA clone).

In a typical approach, genomic DNA or cDNA libraries constructed fromother organisms, e.g. microorganisms capable of converting of a givencarbon source such as e.g. glucose into biomass, in particular otherGluconobacter species may be screened.

For example, Gluconobacter strains may be screened for homologouspolynucleotides by Northern blot analysis. Upon detection of transcriptshomologous to polynucleotides according to the invention, DNA librariesmay be constructed from RNA isolated from the appropriate strain,utilizing standard techniques well known to those of skill in the art.Alternatively, a total genomic DNA library may be screened using a probehybridisable to a polynucleotide according to the invention.

A nucleic acid molecule of the present invention, such as for instance anucleic acid molecule shown in SEQ ID NO:1 or a fragment or derivativethereof, may be isolated using standard molecular biology techniques andthe sequence information provided herein. For example, using all orportion of the nucleic acid sequence shown in SEQ ID NO:1 as ahybridization probe, nucleic acid molecules according to the inventionmay be isolated using standard hybridization and cloning techniques(e.g., as described in Sambrook, J., Fritsh, E. F., and Maniatis, T.Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring HarborLaboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor,N.Y., 1989).

Furthermore, oligonucleotides corresponding to or hybridisable tonucleotide sequences according to the invention may be prepared bystandard synthetic techniques, e.g., using an automated DNA synthesizer.

The terms “homology” or “percent identity” are used interchangeablyherein. For the purpose of this invention, it is defined here that inorder to determine the percent identity of two amino acid sequences orof two nucleic acid sequences, the sequences are aligned for optimalcomparison purposes (e.g., gaps may be introduced in the sequence of afirst amino acid or nucleic acid sequence for optimal alignment with asecond amino or nucleic acid sequence). The amino acid residues ornucleotides at corresponding amino acid positions or nucleotidepositions are then compared. When a position in the first sequence isoccupied by the same amino acid residue or nucleotide as thecorresponding position in the second sequence, then the molecules areidentical at that position. The percent identity between the twosequences is a function of the number of identical positions shared bythe sequences (i.e., % identity=number of identical positions/totalnumber of positions (i.e., overlapping positions)×100). Preferably, thetwo sequences are the same length.

The skilled person will be aware of the fact that several differentcomputer programs are available to determine the homology between twosequences. For instance, a comparison of sequences and determination ofpercent identity between two sequences may be accomplished using amathematical algorithm. In a preferred embodiment, the percent identitybetween two amino acid sequences is determined using the Needleman andWunsch (J. Mol. Biol. (48): 444-453 (1970)) algorithm which has beenincorporated into the GAP program in the GCG software package (availableat URL accelrys[dot]com), using either a Blossom 62 matrix or a PAM250matrix, and a gap weight of 16, 14, 12, 10, 8, 6 or 4 and a lengthweight of 1, 2, 3, 4, 5 or 6. The skilled person will appreciate thatall these different parameters will yield slightly different results butthat the overall percentage identity of two sequences is notsignificantly altered when using different algorithms.

In yet another embodiment, the percent identity between two nucleotidesequences is determined using the GAP program in the GCG softwarepackage (available at URL accelrys[dot]com), using a NWSgapdna.CMPmatrix and a gap weight of 40, 50, 60, 70 or 80 and a length weight of1, 2, 3, 4, 5 or 6. In another embodiment, the percent identity betweentwo amino acid or nucleotide sequences is determined using the algorithmof E. Meyers and W. Miller (CABIOS, 4: 11-17 (1989) which has beenincorporated into the ALIGN program (version 2.0) (available at URLvega[dot]igh[dot]cnrs[dot]fr[slash]bin[slash]align-guess[dot]cgi) usinga PAM120 weight residue table, a gap length penalty of 12 and a gappenalty of 4.

The nucleic acid and protein sequences of the present invention mayfurther be used as a “query sequence” to perform a search against publicdatabases to, for example, identify other family members or relatedsequences. Such searches may be performed using the BLASTN and BLASTXprograms (version 2.0) of Altschul, et al. (1990) J. Mol. Biol.215:403-10. BLAST nucleotide searches may be performed with the BLASTNprogram, score=100, word length=12 to obtain nucleotide sequenceshomologous to the nucleic acid molecules of the present invention. BLASTprotein searches may be performed with the BLASTX program, score=50,word length=3 to obtain amino acid sequences homologous to the proteinmolecules of the present invention. To obtain gapped alignments forcomparison purposes, Gapped BLAST may be utilized as described inAltschul et al., (1997) Nucleic Acids Res. 25 (17): 3389-3402. Whenutilizing BLAST and Gapped BLAST programs, the default parameters of therespective programs (e.g., BLASTX and BLASTN) may be used. See URLncbi[dot]nlm[dot]nih[dot]gov.

In another preferred embodiment, an isolated nucleic acid molecule ofthe invention comprises a nucleic acid molecule which is the complementof a nucleotide sequence as of the present invention, such as forinstance the sequence shown in SEQ ID NO:1. A nucleic acid molecule,which is complementary to a nucleotide sequence disclosed herein, is onethat is sufficiently complementary to a nucleotide sequence shown in SEQID NO:1 such that it may hybridize to said nucleotide sequence therebyforming a stable duplex.

In a further preferred embodiment, a nucleic acid of the invention asshown in SEQ ID NO:1 or the complement thereof contains at least onemutation leading to a gene product with modified function/activity. Theat least one mutation may be introduced by methods described herein. Inone aspect, the at least one mutation leads to a GMS 08 protein whosefunction and/or activity compared to the wild type counterpart isenhanced or improved. Methods for introducing such mutations are wellknown in the art.

The term “increase” of activity as used herein encompasses increasingactivity of one or more polypeptides in the producing organism, which inturn are encoded by the corresponding polynucleotides described herein.There are a number of methods available in the art to accomplishincrease of activity of a given protein, in this case the GMS 08protein. In general, the specific activity of a protein may be increasedor the copy number of the protein may be increased. The term increase ofactivity or equivalent expressions also encompasses the situationwherein GMS 08 protein activity is introduced in a cell that did notcontain this activity before, e.g. by introducing a gene encoding GMS 08in a cell that did not contain an equivalent of this gene before, orthat could not express an active form of the corresponding proteinbefore.

To facilitate such an increase, the copy number of the genescorresponding to the polynucleotides described herein may be increased.Alternatively, a strong promoter may be used to direct the expression ofthe polynucleotide. In another embodiment, the promoter, regulatoryregion and/or the ribosome binding site upstream of the gene can bealtered to increase the expression. The expression may also be enhancedor increased by increasing the relative half-life of the messenger RNA.In another embodiment, the activity of the polypeptide itself may beincreased by employing one or more mutations in the polypeptide aminoacid sequence, which increase the activity. For example, altering theaffinity of the polypeptide for its corresponding substrate may resultin improved activity. Likewise, the relative half-life of thepolypeptide may be increased. In either scenario, that being enhancedgene expression or increased activity, the improvement may be achievedby altering the composition of the cell culture media and/or methodsused for culturing. “Enhanced expression” or “improved activity” as usedherein means an increase of at least 5%, 10%, 25%, 50%, 75%, or even100%, compared to a wild-type protein, polynucleotide, gene; or theactivity and/or the concentration of the protein present before thepolynucleotides or polypeptides are enhanced and/or improved. Theactivity of the GMS 08 protein may also be enhanced by contacting theprotein with a specific or general enhancer of its activity.

Another aspect of the invention pertains to vectors, containing anucleic acid encoding a protein according to the invention or afunctional equivalent or portion thereof. As used herein, the term“vector” refers to a nucleic acid molecule capable of transportinganother nucleic acid to which it has been linked. One type of vector isa “plasmid”, which refers to a circular double stranded DNA loop intowhich additional DNA segments may be ligated. Another type of vector isa viral vector, wherein additional DNA segments may be ligated into theviral genome. Certain vectors are capable of autonomous replication in ahost cell into which they are introduced (e.g., bacterial vectors havinga bacterial origin of replication). Other vectors are integrated intothe genome of a host cell upon introduction into the host cell, andthereby are replicated along with the host genome.

Moreover, certain vectors are capable of directing the expression ofgenes to which they are operatively linked. Such vectors are referred toherein as “expression vectors”. In general, expression vectors ofutility in recombinant DNA techniques are often in the form of plasmids.The terms “plasmid” and “vector” can be used interchangeably herein asthe plasmid is the most commonly used form of vector. However, theinvention is intended to include such other forms of expression vectors,such as viral vectors (e.g., replication defective retroviruses,adenoviruses and adeno-associated viruses), which serve equivalentfunctions.

The recombinant vectors of the invention comprise a nucleic acid of theinvention in a form suitable for expression of the nucleic acid in ahost cell, which means that the recombinant expression vector includesone or more regulatory sequences, selected on the basis of the hostcells to be used for expression, which is operatively linked to thenucleic acid sequence to be expressed. Within a recombinant expressionvector, “operatively linked” is intended to mean that the nucleotidesequence of interest is linked to the regulatory sequence(s) in a mannerwhich allows for expression of the nucleotide sequence (e.g., in an invitro transcription/translation system or in a host cell when the vectoris introduced into the host cell). The term “regulatory sequence” isintended to include promoters, enhancers and other expression controlelements (e.g., attenuator). Such regulatory sequences are described,for example, in Goeddel; Gene Expression Technology: Methods inEnzymology 185, Academic Press, San Diego, Calif. (1990). Regulatorysequences include those which direct constitutive or inducibleexpression of a nucleotide sequence in many types of host cells andthose which direct expression of the nucleotide sequence only in acertain host cell (e.g. tissue-specific regulatory sequences). It willbe appreciated by those skilled in the art that the design of theexpression vector can depend on such factors as the choice of the hostcell to be transformed, the level of expression of protein desired, etc.The expression vectors of the invention may be introduced into hostcells to thereby produce proteins or peptides, encoded by nucleic acidsas described herein, including, but not limited to, mutant proteins,fragments thereof, variants or functional equivalents thereof, andfusion proteins, encoded by a nucleic acid as described herein, e.g.,GMS 08 proteins, mutant forms of GMS 08 proteins, fusion proteins andthe like.

The recombinant expression vectors of the invention may be designed forexpression of GMS 08 proteins in a suitable microorganism. For example,a protein according to the invention may be expressed in bacterial cellssuch as strains belonging to the genera Gluconobacter, Gluconacetobacteror Acetobacter. Expression vectors useful in the present inventioninclude chromosomal-, episomal- and virus-derived vectors e.g., vectorsderived from bacterial plasmids, bacteriophage, and vectors derived fromcombinations thereof, such as those derived from plasmid andbacteriophage genetic elements, such as cosmids and phagemids.

The DNA insert may be operatively linked to an appropriate promoter,which may be either a constitutive or inducible promoter. The skilledperson will know how to select suitable promoters. The expressionconstructs may contain sites for transcription initiation, termination,and, in the transcribed region, a ribosome binding site for translation.The coding portion of the mature transcripts expressed by the constructsmay preferably include an initiation codon at the beginning and atermination codon appropriately positioned at the end of the polypeptideto be translated.

Vector DNA may be introduced into suitable host cells via conventionaltransformation or transfection techniques. As used herein, the terms“transformation”, “transconjugation” and “transfection” are intended torefer to a variety of art-recognized techniques for introducing foreignnucleic acid (e.g., DNA) into a host cell, including calcium phosphateor calcium chloride co-precipitation, DEAE-dextran-mediatedtransfection, transduction, infection, lipofection, cationiclipidmediated transfection or electroporation. Suitable methods fortransforming or transfecting host cells may be found in Sambrook, et al.(supra), Davis et al., Basic Methods in Molecular Biology (1986) andother laboratory manuals.

In order to identify and select cells which have integrated the foreignDNA into their genome, a gene that encodes a selectable marker (e.g.,resistance to antibiotics) is generally introduced into the host cellsalong with the gene of interest. Preferred selectable markers includethose that confer resistance to drugs, such as kanamycin, tetracycline,ampicillin and streptomycin. A nucleic acid encoding a selectable markeris preferably introduced into a host cell on the same vector as thatencoding a protein according to the invention or can be introduced on aseparate vector such as, for example, a suicide vector, which cannotreplicate in the host cells. Cells stably transfected with theintroduced nucleic acid can be identified by drug selection (e.g., cellsthat have incorporated the selectable marker gene will survive, whilethe other cells die).

The invention provides also an isolated polypeptide having the aminoacid sequence shown in SEQ ID NO:2 or an amino acid sequence obtainableby expressing a polynucleotide of the present invention, such as forinstance a polynucleotide sequence shown in SEQ ID NO:1 in anappropriate host.

Polypeptides according to the invention may contain only conservativesubstitutions of one or more amino acids in the amino acid sequencerepresented by SEQ ID NO:2 or substitutions, insertions or deletions ofnon-essential amino acids. Accordingly, a non-essential amino acid is aresidue that may be altered in the amino acid sequences shown in SEQ IDNO:2 without substantially altering the biological function. Forexample, amino acid residues that are conserved among the proteins ofthe present invention, are predicted to be particularly unamenable toalteration. Furthermore, amino acids conserved among the proteinsaccording to the present invention and other GMS 08 proteins are notlikely to be amenable to alteration.

The term “conservative substitution” is intended to mean that asubstitution in which the amino acid residue is replaced with an aminoacid residue having a similar side chain. These families are known inthe art and include amino acids with basic side chains (e.g., lysine,arginine and histidine), acidic side chains (e.g., aspartic acid,glutamic acid), uncharged polar side chains (e.g., glycine, asparagine,glutamine, serine, threonine, tyrosine, cysteine), non-polar side chains(e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine,methionine, tryptophan), beta-branched side chains (e.g., threonine,valine, isoleucine) and aromatic side chains (e.g., tyrosine,phenylalanine, tryptophan, histidine).

As mentioned above, the polynucleotides of the invention may be utilizedin the genetic engineering of a suitable host cell to make it better andmore efficient in the bioconversion of a carbon source such as e.g.glucose to biomass, i.e. reduction of carbon source diversion throughoutthe bioconversion process.

According to the invention a genetically engineered/recombinant hostcell (also referred to as recombinant cell or transformed cell) may beproduced carrying such a modified polynucleotide wherein the function ofthe linked protein is significantly modified in comparison to awild-type cell such that the yield and/or productivity of biomass from acarbon source such as e.g. glucose is improved. The host cell may beselected from a microorganism capable of converting a given carbonsource such as e.g. glucose into biomass, in particular Gluconobacteroxydans, preferably G. oxydans DSM 17078.

A “transformed cell” or “recombinant cell” is a cell into which (or intoan ancestor of which) has been introduced, by means of recombinant DNAtechniques, a nucleic acid according to the invention, or wherein theactivity of the GMS 08 protein has been increased and/or enhanced.Suitable host cells include cells of microorganisms capable ofconverting a given carbon source such as e.g. glucose into biomass. Inparticular, these include strains from the genera Pseudomonas, Pantoea,Escherichia, Corynebacterium, Ketogulonicigenium and acetic acidbacteria like e.g., Gluconobacter, Acetobacter or Gluconacetobacter,preferably Acetobacter sp., Acetobacter aceti, Gluconobacter frateurii,Gluconobacter cerinus, Gluconobacter thailandicus, Gluconobacteroxydans, more preferably G. oxydans, most preferably G. oxydans DSM17078.

Improved gene expression may also be achieved by modifying the GMS 08gene, e.g., by introducing one or more mutations into the GMS 08 genewherein said modification leads to a GMS 08 protein with a functionwhich is significantly improved in comparison to the wild-type protein.

Therefore, in one other embodiment, the polynucleotide carrying the atleast one mutation is derived from a polynucleotide as represented bySEQ ID NO:1 or equivalents thereof.

A mutation as used herein may be any mutation leading to a morefunctional or more stable polypeptide, e.g. more functional or morestable GMS 08 gene products. This may include for instance an alterationin the genome of a microorganism, which improves the synthesis of GMS 08or leads to the expression of a GMS 08 protein with an altered aminoacid sequence whose function compared with the wild type counterparthaving a non-altered amino acid sequence is improved and/or enhanced.The improvement may occur at the transcriptional, translational orpost-translational level.

The alteration in the genome of the microorganism may be obtained e.g.by replacing through a single or double crossover recombination a wildtype DNA sequence by a DNA sequence containing the alteration. Forconvenient selection of transformants of the microorganism with thealteration in its genome the alteration may, e.g. be a DNA sequenceencoding an antibiotic resistance marker or a gene complementing apossible auxotrophy of the microorganism. Mutations include, but are notlimited to, deletion-insertion mutations.

An alteration in the genome of the microorganism leading to a morefunctional polypeptide may also be obtained by randomly mutagenizing thegenome of the microorganism using e.g. chemical mutagens, radiation ortransposons and selecting or screening for mutants which are better ormore efficient producers of biomass. Standard methods for screening andselection are known to the skilled person.

In a specific embodiment, it is desired to knockout or suppress arepressor of the GMS 08 gene of the present invention, i.e., wherein itsrepressor gene expression is artificially suppressed in order to improvethe yield and/or efficiency of biomass production when introduced into asuitable host cell. Methods of providing knockouts as well asmicroorganisms carrying such suppressed genes are well known in the art.The suppression of the repressor gene may be induced by deleting atleast a part of the repressor gene or the regulatory region thereof. Asused herein, “suppression of the gene expression” includes complete andpartial suppression, as well as suppression under specific conditionsand also suppression of the expression of either one of the two alleles.

The aforementioned mutagenesis strategies for GMS 08 proteins may resultin increased yield and/or production of biomass. This list is not meantto be limiting; variations on these mutagenesis strategies will bereadily apparent to one of ordinary skill in the art. By thesemechanisms, the nucleic acid and protein molecules of the invention maybe utilized to generate microorganisms such as Gluconobacter oxydans orrelated strains of bacteria expressing mutated GMS 08 nucleic acid andprotein molecules such that the yield, efficiency and/or productivity ofbiomass production from a carbon source such as e.g. glucose isimproved.

Biomass concentration can be measured using several methods known to theperson skilled in the art, such as e.g. measuring the optical density ofthe respective cell suspensions at for instance a wavelength of 600 nm(OD₆₀₀), or measuring either the wet- or dry-cell mass concentration orby counting the numbers of cells of the respective cell suspension. Suchmethods of measurement are known in the art. Thus, the cell dry weight(CDW) [g/l] may be for instance measured on a dried and tarednitrocellulose filter with a pore size of e.g. 0.45 μm on which theculture broth is filtrated. After washing the filter with water, theweight of the dried filter is again determined and the CDW calculated asfollows:CDW=m(dried filter after broth filtration)−m(dried filter before brothfiltration)

In one aspect of the invention, microorganisms (in particular from thegenera of Gluconobacter, Gluconacetobacter and Acetobacter) are providedthat are able to perform such improved bioconversion. When measured by amethod as described herein these organisms were found to have animproved capability to produce biomass from a carbon source such as e.g.glucose. Such may be achieved by increasing the activity of a GMSpolypeptide, preferably a GMS 08 polypeptide. The yield of biomassproduced from a carbon source, such as for instance glucose, whenmeasured according to this method after an incubation period of 24 hoursmay be about 0.1 g or more dry biomass/g carbon source, preferably about0.2 g or more dry biomass/g carbon source, or even about 0.3 g or moredry biomass/g carbon source, such as for instance about 0.4 g, 0.5 g,0.6 g, 0.7 g, 0.8 g or 1.0 g or more dry biomass/g carbon source.Preferably, the carbon source is glucose.

The recombinant microorganism carrying e.g. a modified GMS 08 gene andwhich is able to produce biomass from a carbon source such as e.g.glucose in significantly higher yield, productivity, and/or efficiencymay be cultured in an aqueous medium supplemented with appropriatenutrients under aerobic conditions. The cultivation may be conducted inbatch, fed-batch, semi-continuous or continuous mode. The cultivationperiod may vary depending on for instance the host, pH, temperature andnutrient medium to be used, and is preferably about 1 to about 10 dayswhen run in batch or fed-batch mode. The cultivation may be conducted atfor instance a pH of about 4.0 to about 9.0, preferably about 5.0 toabout 8.0. The preferred temperature range for carrying out thecultivation is from about 13° C. to about 36° C., preferably from about18° C. to about 33° C. Usually, the culture medium may contain besidese.g. D-glucose as main carbon source other assimilable carbon sources,e.g., glycerol, D-mannitol, D-sorbitol, L-sorbose, erythritol, ribitol,xylitol, arabitol, inositol, dulcitol, D-ribose, D-fructose, sucrose andethanol, preferably D-sorbitol, D-mannitol, D-fructose, glycerol andethanol; and digestible nitrogen sources such as organic substances,e.g., peptone, yeast extract, baker's yeast, urea, amino acids, and cornsteep liquor. Various inorganic substances may also be used as nitrogensources, e.g., nitrates and ammonium salts. Furthermore, the culturemedium usually may contain inorganic salts, e.g., magnesium sulfate,manganese sulfate, potassium phosphate, and calcium carbonate.

The nucleic acid molecules, polypeptides, vectors, primers, andrecombinant microorganisms described herein may be used in one or moreof the following methods: identification of Gluconobacter oxydans andrelated organisms; mapping of genomes of organisms related toGluconobacter oxydans; identification and localization of Gluconobacteroxydans sequences of interest; evolutionary studies; determination ofGMS 08 protein regions required for function; modulation of a GMS 08protein activity or function; modulation of the activity of a GMSpathway; and modulation of cellular production of biomass from a carbonsource such as e.g. glucose.

The invention provides methods for screening molecules which modulatethe activity of a GMS 08 protein, either by interacting with the proteinitself or a substrate or binding partner of the GMS 08 protein, or bymodulating the transcription or translation of a GMS 08 nucleic acidmolecule of the invention. In such methods, a microorganism expressingone or more GMS 08 proteins of the invention is contacted with one ormore test compounds, and the effect of each test compound on theactivity or level of expression of the GMS 08 protein is assessed.

The biological, enzymatic or other activity of GMS proteins can bemeasured by methods well known to a skilled person, such as, forexample, by incubating a cell fraction containing the GMS 08 protein inthe presence of its substrate, electron acceptor(s) or donor(s)including phenazine methosulfate (PMS), dichlorophenol-indophenol(DCIP), NAD, NADH, NADP, NADPH, which consumption can be directly orindirectly measured by photometric, colorimetric or fluorimetricmethods, and other inorganic components which might be relevant for thedevelopment of the activity. Thus, for example, the activity ofmembrane-bound D-glucose dehydrogenase can be measured in an assay wheremembrane fractions containing this enzyme are incubated in the presenceof phosphate buffer at pH 6, D-glucose and the artificial electronacceptors DCIP and PMS. The rate of consumption of DCIP can be measuredat 600 nm, and is directly proportional to the D-glucose dehydrogenaseactivity present in the membrane fraction.

Furthermore, the activity of gluconokinase can be measured in an assaywhere soluble fractions containing this enzyme are incubated in thepresence of glycylclycine buffer at pH 8, ATP, D-gluconic acid, MgCl2,NADP+, 6-phophsgluconate dehydrogenase. The change of the absorbance ofreduced NADP can be measured at 340 nm (see also Izu et al.,Purification and characterization of the Escherichia colithermoresistant glucokinase encoded by the gntK gene, FEBS Lett. 1996Sep. 23; 394(1):14-6.)

Thus, the present invention is directed to the use of a polynucleotide,polypeptide, vector, primer and recombinant microorganism as describedherein in the production of biomass, i.e., the bioconversion of a carbonsource such as e.g. glucose into biomass. In a preferred embodiment, amodified polynucleotide, polypeptide, vector and recombinantmicroorganism as described herein is used for improving the yield,productivity, and/or efficiency of said biomass production.

The terms “production” or “productivity” are art-recognized and includethe amount of biomass formed within a given time and a given cultivationvolume (e.g., kg product per hour per liter) from a given amount orconcentration of a carbon source such as e.g. glucose. The term“efficiency of production” includes the time required for a particularlevel of production to be achieved (for example, how long it takes forthe cell to attain a particular rate of output of a product). The term“yield” is art-recognized and includes the efficiency of the conversionof the carbon source into biomass. This is generally written as, forexample, kg biomass per kg carbon source. By “increasing the yieldand/or production of biomass” it is meant that in a given amount ofculture over a given amount of time the biomass is increased. Bymeasuring the increase in biomass- and decrease in carbon sourceconcentration in a growing culture, one can calculate the yield ofbiomass on consumed carbon source; i.e. the weight of biomass obtainedby bioconverting a determined weight of carbon source such as e.g.glucose, defined as kg biomass per kg carbon source consumed. Todetermine the consumption of carbon source, the residual amount ofcarbon source in the growth medium can be measured by methods well knownin the art (e.g. HPLC). The increase of biomass can be measured bymethods well known in the art (e.g. optical density at 600 nm, ormeasurement of dry weight of a sample).

The terms “biosynthesis” or a “biosynthetic pathway” are art-recognizedand include the synthesis of a compound/product, preferably an organiccompound, by a cell from intermediate compounds in what may be amultistep and highly regulated process. The term “bioconversion” isart-recognized and includes the conversion of a carbon source such ase.g. glucose into a product, i.e. biomass, by means of one or morebiosynthetic step(s) which involve one or more enzyme(s) and/ortransporter(s). The language “metabolism” is art-recognized and includesthe totality of the biochemical reactions that take place in anorganism. The metabolism of a particular compound, then, (e.g., themetabolism of an amino acid such as glycine) comprises the overallbiosynthetic, modification, and degradation pathways in the cell relatedto this compound. The language “transport” or “import” is art-recognizedand includes the facilitated movement of one or more molecules across acellular membrane through which the molecule would otherwise either beunable to pass or be passed inefficiently.

In one preferred embodiment, the present invention is related to aprocess for the production of biomass from a carbon source such as e.g.glucose wherein a modified polynucleotide sequence as described above isintroduced into a suitable microorganism and the recombinantmicroorganism is cultured under conditions that allow the production ofbiomass in high productivity, yield, and/or efficiency.

Recombinant microorganisms according to the present invention carryinge.g. a modified GMS gene, in particular a modified GMS 08 gene, andwhich are able to produce biomass from a carbon source such as e.g.glucose in significantly higher yield, productivity, and/or efficiencymay advantageously be used in a number of applications. One particularlysuited application is a method for the production of Vitamin C and/orintermediates thereof such like 2-keto-L-gulonic acid (2-KGA).

Thus, it is an aspect of the present invention to provide a process forthe production of Vitamin C and/or 2-KGA wherein a nucleotide accordingto the invention or a modified polynucleotide sequence as describedabove is introduced into a suitable microorganism as described abovewherein a suitable carbon source such as e.g. glucose is efficientlyconverted into biomass, the recombinant microorganism is cultured underconditions that allow the production of Vitamin C and/or 2-KGA in highproductivity, yield, and/or efficiency, the produced fermentationproduct is isolated from the culture medium and optionally furtherpurified.

The carbon sources used for the production of (1) biomass and (2)Vitamin C and/or 2-KGA may be the same or may differ. In one preferredembodiment, the carbon source(s) used for the production of biomass isdifferent from the carbon source(s) used for the direct production ofVitamin C and/or 2-KGA. These two different carbon sources may be usedsimultaneously or sequentially, wherein a first carbon source would beused for the production of biomass, and this biomass would then be usedto convert a second carbon source into Vitamin C and/or 2-KGA.

A suitable carbon source that can be converted directly into Vitamin Cand/or 2-KGA may be selected from the D-glucose or D-sorbitolmetabolization pathway such as, for example, D-glucose, D-sorbitol,L-sorbose, L-sorbosone, D-gluconate, 2-keto-D-gluconate or2,5-diketo-gluconate or mixtures thereof. Preferably, the substrate isselected from for instance D-glucose, D-sorbitol, L-sorbose, L-sorbosoneor mixtures thereof, more preferably from D-glucose, D-sorbitol,L-sorbose or mixtures thereof, and most preferably from D-sorbitol,L-sorbose or mixtures thereof.

Vitamin C as used herein may be any chemical form of L-ascorbic acidfound in aqueous solutions, such as for instance undissociated, in itsfree acid form or dissociated as an anion. The solubilized salt form ofL-ascorbic acid may be characterized as the anion in the presence of anykind of cations usually found in fermentation supernatants, such as forinstance potassium, sodium, ammonium, or calcium. Also included may beisolated crystals of the free acid form of L-ascorbic acid. On the otherhand, isolated crystals of a salt form of L-ascorbic acid are called bytheir corresponding salt name, i.e. sodium ascorbate, potassiumascorbate, calcium ascorbate and the like.

Conversion of a suitable carbon source into Vitamin C and/or 2-KGA inconnection with the above process using a microorganism means that theconversion of the carbon source resulting in Vitamin C and/or 2-KGA isperformed by the microorganism, i.e. the carbon source may be directlyconverted into Vitamin C and/or 2-KGA. Said microorganism is culturedunder conditions which allow such conversion from said carbon source asit is known for the skilled person.

A medium as used herein for the above process using a microorganism maybe any suitable medium for the production of Vitamin C and/or 2-KGA.Typically, the medium is an aqueous medium comprising for instancesalts, substrate(s), and a certain pH.

The term “direct conversion” and the like is intended to mean that amicroorganism is capable of the conversion of a certain carbon sourceinto the specified product by means of one or more biological conversionsteps, without the need of any additional chemical conversion step. Forinstance, the term “direct conversion of D-sorbitol into Vitamin C” isintended to describe a process wherein a microorganism is producingVitamin C and wherein D-sorbitol is offered as a carbon source withoutthe need of an intermediate chemical conversion step. A singlemicroorganism capable of directly fermenting Vitamin C is preferred.

This invention is further illustrated by the following examples whichshould not be construed as limiting. The contents of all references,patent applications, patents and published patent applications, citedthroughout this application are hereby incorporated by reference.

EXAMPLES Example 1 Analytical Methods for Biomass and GlucoseDetermination

For determination of biomass production, cells of G. oxydans were grownat 27° C. for 3 days on MB agar, containing 25 g/l mannitol, 5.0 g/lyeast extract (Difco), 3.0 g/l Bactopeptone (Difco) and 15 g/l agar.Cells were resuspended in 10% glycerol (10 ml per plate) and 1 mlaliquots were stored at −80° C.

A baffled 500 ml shake flask with 100 ml medium No. 5 containing 50 g/lD-glucose, 0.5 g/l glycerol, 15 g/l yeast extract (Difco), 2.5 g/lMgSO₄.7H₂O, 0.3 g/l KH₂PO₄, 15 g/l CaCO₃ and 1 drop antifoam wasinoculated with a 1 ml aliquot and incubated at 30° C. and 180 rpm in ashaker for 48 h. The optical density at 600 nm (OD₆₀₀) was determinedusing a Spectronic 4001/N spectrophotometer and an identical medium No.5 flask was then inoculated with this culture, such that the start OD₆₀₀in the second flask was 0.25. This flask was then further incubated at30° C., 180 rpm for another 80 h with samples of 3 ml taken every 12 hfor analysis of biomass and glucose concentrations as follows:

Production of biomass was determined via measurement of the dry weightof the sample. Reaction tubes were pre-dried at 40° C. under vacuum for48 h and the weight of the empty tubes measured [w1]. The sample wasadded and the weight of the full tube determined [w2]. 0.1 ml 18.5% HClwas added to dissolve the CaCO₃. The tubes were subsequently centrifugedfor 3 min at 13000 rpm. The supernatant was discarded, 0.5 ml of waterwas added and the pellet was resuspended. The tube was centrifuged againfor 3 min at 13000 rpm and the supernatant was discarded. The pellet wasdried at 40° C. under vacuum for 48 h and the tube containing the pelletagain weighted [w3]. The concentration of biomass [B] in the sample wascalculated as follows:(w3−w1)/w2−w1)×1000=concentration of biomass [g/kg]

The amount or concentration of glucose [G] was measured by HPLC on anHewlett-Packard 1100 instrument using an Aminex-HPX-78H (300×7.8 mm)column (Biorad, Reinach, Switzerland) combined with aLiChrospher-100—RP18, 5 μm precolumn (Merck, Darmstadt, Germany). Themobile phase was 0.004 M sulfuric acid, pumped at a flow rate of 0.6ml/min. A refractive index detector was used to monitor the signal.External standard calibration was applied based on peak areas.

The yield, i.e. the amount of biomass (dry weight) obtained fromconversion of D-glucose [g biomass/g D-glucose] after a given time wascalculated as follows, wherein (t1) defines the concentration of biomassand D-glucose, respectively, measured during or at the end ofcultivation, for instance after 24 or 48 h, and (t0) defines therespective concentrations at the beginning of the cultivation (seeabove):[B(t1)−B(t0)]/[G(t1)−G(t0)]=yield of biomass on consumed glucose [g/g]

The volumetric biomass productivity [g/kg/h], i.e. the amount of biomassproduced per liter of culture and per time unit was calculated asfollows:[B(t1)−B(t0)]/(t0−t1)=volumetric biomass productivity [g/kg/h]

Example 2 Preparation of Chromosomal DNA and Amplification of DNAFragment by PCR

Chromosomal DNA of Gluconobacter oxydans DSM 17078 was prepared from thecells cultivated at 30° C. for 1 day in mannitol broth (MB) liquidmedium consisting of 25 g/l mannitol, 5 g/l of yeast extract (Difco),and 3 g/l of Bactopeptone (Difco) by the method described by Sambrook etal (1989) “Molecular Cloning: A Laboratory Manual/Second Edition”, ColdSpring Harbor Laboratory Press).

A DNA fragment was prepared by PCR with the chromosomal DNA preparedabove and a set of primers, Pf (SEQ ID NO:3) and Pr (SEQ ID NO:4). Forthe reaction, the Expand High Fidelity PCR kit (Roche Diagnostics) and10 ng of the chromosomal DNA was used in total volume of 100 μlaccording to the supplier's instruction to have the PCR productcontaining GMS 08 DNA sequence (SEQ ID NO:1). The PCR product wasrecovered from the reaction and its correct sequence confirmed.

Example 3 Overexpression of the GMS 08 Gene in G. oxydans DSM 17078-ΔGMS01

G. oxydans DSM 17078-ΔGMS 01 was obtained by gene disruption using thesacB selection system (Link et al., J. Bacteriol., 179(20):6228-37,1997; Schafer et al., Gene 22; 145(1):69-73, 1994). For this, a PCRproduct with an in-frame deleted GMS 01 gene was constructed bylong-flanking homology PCR using genomic DNA obtained in Example 2 astemplate. The 5′-portion of the GMS 01 gene was amplified by PCR usingprimers coPCR-gdh-5F (SEQ ID NO:7) and coPCR-gdh-5R (SEQ ID NO:8),yielding PCR product A. The 3′-portion of the GMS 01 gene was amplifiedby PCR using primers coPCR-gdh-3F (SEQ ID NO:9) and coPCR-gdh-3R (SEQ IDNO:10), yielding PCR product B. In a third PCR reaction, a PCR productcontaining the in-frame deleted GMS 01 gene (SEQ ID NO:11) was obtained,using a 1:1 molar mixture of the PCR products A and B as template andcoPCR-gdh-5F (SEQ ID NO:7) and coPCR-gdh-3R (SEQ ID NO:10) as primers.

The resulting PCR product containing the in-frame deleted GMS 01 genewas digested with PstI and HindIII and cloned into PstI-HindIII-digestedpK19mobsacB vector, resulting in the deletion plasmid pK19mobsacB-ΔGMS01. This plasmid was transformed into G. oxydans DSM 17078 selecting fortransformants on media containing kanamycin. The integration of plasmidpK19mobsacB-ΔGMS 01 was confirmed by PCR analysis. To inducerecombination of the integrated plasmid and replacement of the wild-typeGMS 01 gene by the in-frame deleted GMS 01 gene, kanamycin-resistancecolonies were plated onto media containing 10% sucrose withoutantibiotics. After several days, sucrose-resistant colonies appearedwhich were checked for kanamycin sensitivity and the replacement of thewild-type GMS 01 gene by the in-frame deleted GMS 01 gene by PCRanalysis. One such mutant was found and named G. oxydans DSM 17078-ΔGMS01.

For overexpression of GMS 08, the PCR product obtained in Example 2 wasamplified using the primers gkGoxBglII_R (SEQ ID NO:5) and gkGoxXhoI_F(SEQ ID NO:6) and cloned into the expression vector pBBR1MCS2 (Kovach etal., “pBBRIMCS: a broad-host-range cloning vector”, Biotechniques, 1994May; 16(5):800-2; and Kovach et al., “Four new derivatives of thebroad-host-range cloning vector pBBR1MCS, carrying differentantibiotic-resistance cassettes”, Gene, 1995 Dec. 1; 166(1): 175-6),containing a kanamycin resistance cassette, resulting in pBBR1MCS2-GMS08. The gene was subcloned from pBBR1MCS2-GMS 08 into pBBR1MCS4 (Kovachet al., 1994 and 1995), which contains an ampicillin resistancecassette, by digesting pBBR1MCS2-GMS 08 with the restrictionendonucleases SacI and KpnI to excise the GMS 08 gene. The gene wascloned into SacI-KpnI-digested pBBR1MCS4 to give plasmid pBBR1MCS4-GMS08. The plasmid pBBR1MCS4-GMS 08 was used to transform G. oxydans DSM17078-ΔGMS 01 to obtain a strain which overexpresses GMS 08 gene and inaddition is disrupted in the GMS 01 gene. The strain was named G.oxydans DSM 17078-ΔGMS 01/pBBR1MCS4-GMS 08. Using an enzymatic assay theoverexpression of GMS 08 in the background of G. oxydans DSM 17078-ΔGMS01 was confirmed.

Example 4 Production of Biomass from D-Glucose in Liquid Cultures

Cells of G. oxydans DSM 17078-ΔGMS 01 and G. oxydans DSM 17078-ΔGMS01/pBBR1MCS4-GMS 08 were cultivated as described above and thevolumetric biomass productivity determined (see Example 1), wherein(t1)=71 h. The results are depicted in Table 1.

TABLE 1 Production of biomass from D-glucose Volumetric biomass Strainproductivity [g/kg/h] DSM 17078-ΔGMS 01 0.035 DSM 17078-ΔGMS 01/ 0.054pBBR1MCS4-GMS 08

Example 5 Presence of the GMS 08 Gene and Equivalents in Other Organisms

The presence of SEQ ID NO:1 and/or equivalents in other organisms thanthe ones disclosed herein before, e.g. organisms as mentioned in Table2, may be determined by a simple DNA hybridization experiment.

Strains of Acetobacter aceti subsp. xylinum IFO 13693 and IFO 13773 aregrown at 27° C. for 3 days on No. 350 medium containing 5 g/lBactopeptone (Difco), 5 g/l yeast extract (Difco), 5 g/l glucose, 5 g/lmannitol, 1 g/l MgSO₄.7H₂O, 5 ml/l ethanol, and 15 g/l agar. All otherAcetobacter, Gluconacetobacter and all Gluconobacter strains are grownat 27° C. for 3 days on mannitol broth (MB) agar medium containing 25 μlmannitol, 5 g/l yeast extract (Difco), 3 g/l Bactopeptone (Difco), and18 g/l agar (Difco). E. coli K-12 is grown on Luria Broth agar medium.The other strains are grown on medium recommended by the suppliers oraccording to methods known in the art. Genomic DNA is extracted asdescribed by e.g. Sambrook et al., 1989, “Molecular Cloning: ALaboratory Manual/Second Edition”, Cold Spring Harbor Laboratory Press)from a suitable organism as, e.g. mentioned in Table 2.

Genomic DNA preparations are digested with restriction enzymes such asEcoRI or HindIII, and 1 μg of the DNA fragments are separated by agarosegel electrophoresis (1% agarose). The gel is treated with 0.25 N HCl for15 min and then 0.5 N NaOH for 30 min, and then blotted ontonitrocellulose or a nylon membrane with Vacuum Blotter Model 785(BIO-RAD Laboratories AG, Switzerland) according to the instruction ofthe supplier. The resulting blot is then brought into contact/hybridizedwith a solution wherein the probe, such as e.g. a DNA fragment with SEQID NO:1 sequence or a DNA fragment containing the part or whole of theSEQ ID NO:1 sequence to detect positive DNA fragment(s) from a testorganism. A DIG-labeled probe, e.g. SEQ ID NO:1, may be preparedaccording to Example 1 by using the PCR-DIG labeling kit (RocheDiagnostics) and a set of primers, SEQ ID NO:3 and SEQ ID NO:4. A resultof such a blot is depicted in Table 2.

The hybridization may be performed under stringent or highly stringentconditions. A preferred, non-limiting example of such conditions arehybridization in 6× sodium chloride/sodium citrate (SSC) at about 45°C., followed by one or more washes in 1×SSC, 0.1% SDS at 50° C.,preferably at 55° C., more preferably at 60° C. and even more preferablyat 65° C. Highly stringent conditions include, for example, 2 h to 4days incubation at 42° C. in a solution such as DigEasyHyb solution(Roche Diagnostics GmbH) with or without 100 μg/ml salmon sperm DNA, ora solution comprising 50% formamide, 5×SSC (150 mM NaCl, 15 mM trisodiumcitrate), 0.02% sodium dodecyl sulfate, 0.1% N-lauroylsarcosine, and 2%blocking reagent (Roche Diagnostics GmbH), followed by washing thefilters twice for 5 to 15 min in 2×SSC and 0.1% SDS at room temperatureand then washing twice for 15-30 min in 0.5×SSC and 0.1% SDS or 0.1×SSCand 0.1% SDS at 65-68° C. To detect DNA fragments with lower identity tothe probe DNA, final washing steps can be done at lower temperaturessuch as 50-65° C. and for shorter washing time such as 1-15 min.

The genes corresponding to the positive signals within the respectiveorganisms shown in Table 2 can be cloned by a PCR method well known inthe art using genomic DNA of such an organism together with a suitableprimer set, such as e.g. SEQ ID NO:3 and SEQ ID NO:4 under conditions asdescribed in Example 1 or as follows: 5 to 100 ng of genomic DNA is usedper reaction (total volume 50 μl). Expand High Fidelity PCR system(Roche Diagnostics) can be used with reaction conditions consisting of94° C. for 2 min; 30 cycles of (i) denaturation step at 94° C. for 15sec, (ii) annealing step at 60° C. for 30 sec, (iii) synthesis step at72° C. for 0.5 to 5 min depending to the target DNA length (1 min/1 kb);extension at 72° C. for 7 min. Alternatively, one can perform a PCR withdegenerate primers, which can be synthesized based on SEQ ID NO:2 oramino acid sequences as consensus sequences selected by aligning severalamino acid sequences obtained by a sequence search program such asBLASTP (or BLASTX when nucleotide sequence is used as a “querysequence”) to find proteins having a similarity to the protein of SEQ IDNO:2. For PCR using degenerate primers, temperature of the secondannealing step (see above) can be lowered to 55° C., or even to 50-45°C. A result of such an experiment is shown in Table 2.

Samples of the PCR reactions are separated by agarose gelelectrophoresis and the bands are visualized with a transilluminatorafter staining with e.g. ethidium bromide, isolated from the gel and thecorrect sequence is confirmed.

Consensus sequences mentioned above might be amino acid sequencesbelonging to certain categories of several protein domain/familydatabases such as PROSITE (database of protein families and domains),COGs (Cluster of Ortholog Groups), CDD (Conserved Domain Databases),pfam (large collection of multiple sequence alignments and hidden Markovmodels covering many common protein domains and families). Once one canselect certain protein with identical/similar function to the protein ofthis invention from proteins containing domain or family of suchdatabases, corresponding DNA encoding the protein can be amplified byPCR using the protein sequence or its nucleotide sequence when it isavailable in public databases. Following organisms may further providegenes, which can be used as an alternative gene of this invention:Rhodococcus sp. RHA 1, Bradyrhizobium japonicum USDA 110, Sinorhizobiummeliloti 1021, Mesorhizobium loti MAFF303099, Burkholderia mallei ATCC23344, Zymomonas mobilis subsp. mobilis ZM4, and Erwinia carotovorasubsp. astrospetica SCR11043.

Example 6 Overexpression of the GMS 08 Gene and Equivalents in otherOrganisms for Production of Biomass

In order to improve biomass production in a suitable microorganism froma carbon source such as e.g. glucose, the GMS 08 gene and equivalents ase.g. a PCR product obtained in Example 6, referred to hereafter as geneX, can be used in an overexpression system according to Example 2 or canbe cloned into pCR2.1-TOPO (Invitrogen, Carlsbad, Calif., USA) and usedto transform E. coli TG1 to have a Ap^(r) transformant carryingpCR2.1-TOPO-gene X, i.e. carrying a PCR product obtained in Example 4.The insert is amplified with a set of primers, PfNdeI [SEQ ID NO:3 withCCCAT at the 5′-end] and PrHindIII [SEQ ID NO:4 with CCAAGCTT at the5′-end], by PCR. Resulting PCR product is digested with NdeI and HindIIIand the fragment is inserted together with PcrtE-SD (Shine-Dalgamo)fragment (WO 02/099095) digested with XhoI and NdeI into pVK100 (ATCC37156) between the sites of XhoI and HindIII. E. coli TG1 is transformedwith the ligation product to have Tc^(r) transformant carrying plasmidpVK-PcrtE-SD-gene X, which is then used to transform a suitable host,e.g. G. oxydans DSM 17078 by electroporation to have e.g. Tc^(r) G.oxydans DSM 17078/pVK-PcrtE-SD-gene X.

Further modifications including genes involved in the conversion of acarbon source such as e.g. glucose into biomass within said strains maybe generated to improve biomass production within such strains.

Production of biomass from a carbon source such as e.g. glucose usingthe cells of the recombinant cells of e.g. G. oxydans strains DSM 17078and the corresponding wild-type strain are performed according toaccording to Example 4.

In a reaction with 5% glucose as carbon source, the mutant strain G.oxydans DSM 17078-ΔGMS 01/pBBRIMCS4-GMS 08 can produce at least morethan 150% biomass compared to the strain G. oxydans DSM 17078-ΔGMS 01.

TABLE 2 Equivalents of the GMS 08 gene in other organisms. Strain Signal1 Signal 2 Signal 3 G. oxydans DSM 17078 ++++ + + G. oxydans IFO 3293++++ + + G. oxydans IFO 3292 ++++ + + G. oxydans ATCC 621H ++++ + + G.oxydans IFO 12528 ++++ + + G. oxydans G 624 ++++ + + G. oxydans T-100++++ + + G. oxydans IFO 3291 ++++ + + G. oxydans IFO 3255 ++++ + + G.oxydans ATCC 9937 ++++ + + G. oxydans IFO 3244 ++++ + + G. cerinus IFO3266 ++++ + + G. frateurii IFO 3260 ++++ + + G. oxydans IFO 3287++++ + + Acetobacter aceti subsp. orleanus ++ − + IFO 3259 Acetobacteraceti subsp. xylinum ++ − + IFO 13693 Acetobacter aceti subsp. xylinum++ − + IFO 13773 Acetobacter sp. ATCC 15164 ++ − + G. thailandicus NBRC100600 ++ + + Gluconacetobacter liquefaciens ++ + + ATCC 14835Gluconacetobacter polyoxogenes ++ + + NBI 1028 Gluconacetobacterdiazotrophicus ++ + + ATCC 49037 Gluconacetobacter europaeus ++ + + DSM6160 Acetobacter aceti 1023 ++ − + Acetobacter pasteurianus NCI 1193 ++− + Pseudomonas putida ATCC 21812 + − + Pseudomonas aeroginosa PAO1 +− + Pseudomonas fluorescens DSM 50106 + − + Pseudomonas syringae B728a +− + Rhodopseudomonas palustris CGA009 + − + Pantoea citrea 1056R + − +E. coli + − + Saccharomyces cerevisiae − − − Aspergillus niger − − −Mouse − − − Signal 1: Detection of DNA on a blot with genomic DNA ofdifferent strains and SEQ ID NO: 1 as labeled probe. Signal 2: Detectionof DNA of different strains in a PCR reaction using primer pair SEQ IDNO: 3 and SEQ ID NO: 4. Signal 3: Detection of DNA of different strainsin a PCR reaction using degenerate primers. For more explanation referto the text.

The invention claimed is:
 1. A process for production of biomass from acarbon source, the process comprising cultivating a Gluconobactermicroorganism in an aqueous nutrient medium under conditions that allowgrowth on said carbon source, said Gluconobacter microorganism beinggenetically engineered by disruption of a gene encoding a PQQ-dependentglucose dehydrogenase having at least 90% identity to the PQQ-dependentglucose dehydrogenase encoded by SEQ ID NO: 11 and introduction of apolynucleotide comprising a nucleotide sequence encoding a gluconatekinase, wherein the nucleotide sequence is selected from the groupconsisting of: (a) a nucleotide sequence encoding a polypeptidecomprising SEQ ID NO:2; (b) a nucleotide sequence comprising SEQ IDNO:1; (c) a nucleotide sequence obtainable by polymerase chain reactionusing genomic DNA from Gluconobacter as a template and the primer setaccording to SEQ ID NO:3 and SEQ ID NO:4 with an annealing step at 60°C. for 30 sec; and (d) a nucleotide sequence, selected fromGluconobacter, Gluconacetobacter or Acetobacter, the complementarystrand of which hybridizes under highly stringent conditions to thenucleotide sequence as defined in (a), said highly stringent conditionscomprising the steps of incubation of hybridization filters for 2 h to 4days at 42° C. in a solution comprising 50% formamide followed bywashing the filters twice for 5 to 15 minutes in 2×SSC/0.1% SDS at roomtemperature and twice for 5 to 30 minutes in 0.1×SSC/0.1% SDS at 65 to68° C.; wherein a yield of at least 0.2 g biomass per gram glucose isproduced.
 2. A process for production of biomass from a carbon source,the process comprising cultivating a Gluconobacter microorganismgenetically engineered by disruption of a gene encoding a PQQ-dependentglucose dehydrogenase having at least 90% identity to the PQQ-dependentglucose dehydrogenase encoded by SEQ ID NO: 11 and overexpressing anendogenous gene comprising a polynucleotide leading to an improved yieldand/or production of biomass from a carbon source produced by saidmicroorganism, wherein said nucleotide sequence encodes a gluconatekinase and is selected from the group consisting of: (a) a nucleotidesequence encoding a polypeptide comprising SEQ ID NO:2; (b) a nucleotidesequence comprising SEQ ID NO:1; (c) a nucleotide sequence obtainable bypolymerase chain reaction using genomic DNA from Gluconobacter as atemplate and the primer set according to SEQ ID NO:3 and SEQ ID NO:4with an annealing step at 60° C. for 30 sec; and (d) a nucleotidesequence, selected from Gluconobacter, Gluconacetobacter or Acetobacter,the complementary strand of which hybridizes under highly stringentconditions to the nucleotide sequence as defined in (a), said highlystringent conditions comprising the steps of incubation of hybridizationfilters for 2 h to 4 days at 42° C. in a solution comprising 50%formamide followed by washing the filters twice for 5 to 15 minutes in2×SSC/0.1% SDS at room temperature and twice for 5 to 30 minutes in0.1×SSC/0.1% SDS at 65 to 68° C.; wherein a yield of at least 0.2 gbiomass per gram glucose is produced.
 3. A process for production ofbiomass from a carbon source, the process comprising cultivating aGluconobacter microorganism genetically engineered by disruption of agene comprising the nucleotide sequence according to SEQ ID NO:11 andintroduction of a polynucleotide comprising a nucleotide sequenceencoding a gluconate kinase, wherein the nucleotide sequence is selectedfrom the group consisting of: (a) a nucleotide sequence encoding apolypeptide comprising SEQ ID NO:2; (b) a nucleotide sequence comprisingSEQ ID NO:1; (c) a nucleotide sequence obtainable by polymerase chainreaction using genomic DNA from Gluconobacter as a template and theprimer set according to SEQ ID NO:3 and SEQ ID NO:4 with an annealingstep at 60° C. for 30 sec; and (d) a nucleotide sequence, selected fromGluconobacter, Gluconacetobacter or Acetobacter, the complementarystrand of which hybridizes under highly stringent conditions to thenucleotide sequence as defined in (a), said highly stringent conditionscomprising the steps of incubation of hybridization filters for 2 h to 4days at 42° C. in a solution comprising 50% formamide followed bywashing the filters twice for 5 to 15 minutes in 2×SSC/0.1% SDS at roomtemperature and twice for 5 to 30 minutes in 0.1×SSC/0.1% SDS at 65 to68° C.; wherein a yield of at least 0.2 g biomass per gram glucose isproduced.
 4. The process according to claim 3, wherein saidpolynucleotide sequence is present in the form of a vector.
 5. Theprocess according to claim 3, wherein said microorganism is geneticallyaltered in such a way that it leads to an improved yield and/orefficiency of biomass produced from a carbon source by saidmicroorganism.
 6. The process according to claim 3 which is capable ofproducing biomass from glucose in a yield of at least about 0.2 gbiomass/g glucose.
 7. The process according to claim 6, wherein theyield is at least about 0.3 g biomass/g glucose.
 8. The processaccording to claim 3, wherein the polynucleotide is operatively linkedto expression control sequences and transferred into the microorganism.9. The process according to claim 1, wherein the genetically engineeredmicroorganism has increased and/or improved gluconate kinase activitycompared to the non-genetically engineered microorganism.
 10. Theprocess according to claim 9, wherein the polynucleotide isoverexpressed in the genetically engineered microorganism.
 11. Theprocess according to claim 1, wherein the carbon source is selected fromthe group consisting of glucose, sucrose, maltose, starch, cellulose,cellobiose, lactose, isomaltose, dextran, trehalose, and mixturesthereof.
 12. The process according to claim 2, wherein the carbon sourceis selected from the group consisting of glucose, sucrose, maltose,starch, cellulose, cellobiose, lactose, isomaltose, dextran, trehalose,and mixtures thereof.
 13. The process according to claim 3, wherein thecarbon source is selected from the group consisting of glucose, sucrose,maltose, starch, cellulose, cellobiose, lactose, isomaltose, dextran,trehalose, and mixtures thereof.
 14. The process according to claim 1,wherein the microorganism is selected from the group consisting ofGluconobacter frateurii, Gluconobacter cerinus, Gluconobacterthailandicus, and Gluconobacter oxydans.
 15. The process according toclaim 1, wherein the microorganism to be genetically engineered isGluconobacter oxydans DSM
 17078. 16. The process according to claim 2which is capable of producing biomass from glucose in a yield of atleast about 0.2 g biomass/g glucose.